JP4641727B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention relates to a magnetic resonance imaging (hereinafter referred to as MRI) apparatus, and in particular, is caused by propagation of GC vibrations and GC vibrations generated by driving a gradient coil (hereinafter abbreviated as GC). The present invention relates to a technique for reducing vibration of a static magnetic field generation source.

   In general, an MRI apparatus includes a static magnetic field generation source that generates a uniform static magnetic field in an imaging space, a GC that generates a linear gradient magnetic field superimposed on the static magnetic field, and an RF coil that transmits and receives a high-frequency electromagnetic field. . At the time of imaging, a linear gradient magnetic field in the X, Y, and Z axis directions is superimposed on a subject placed in a uniform static magnetic field according to a desired pulse sequence, and the nuclear spin of the subject is magnetized with a high frequency magnetic field pulse of Larmor frequency. Excited. With this excitation, a nuclear magnetic resonance (hereinafter abbreviated as NMR) signal is detected, and for example, a two-dimensional tomographic image of the subject is reconstructed.

 In such an MRI apparatus, in recent years, there is an increasing need for shortening the time required for imaging. To meet this demand, pulse sequences that involve high-speed inversion of gradient magnetic field pulses, such as the fast EPI method, have been put into practical use.

When a pulse current is passed through the GC to generate a gradient magnetic field, a pulsed Lorentz force acts on the conductor of the GC because the GC is placed in a static magnetic field. As a result, the GC vibrates with mechanical distortion. This GC vibration is transmitted to the static magnetic field generation source through the fixing member and the like, and vibrates the static magnetic field generation source. Micron-order vibrations of a static magnetic field source cause temporal fluctuations of the static magnetic field, and as a result, have an adverse effect on blurring and artifacts in MRI images. Further, if the vibration of the GC propagates to the space, it brings about air vibration, that is, noise, and as a result, the anxiety of the subject is increased, and the communication with the operator becomes an obstacle.
For this reason, several techniques for reducing the noise described above have been proposed.

In [Patent Document 1], a noise reduction device is inserted between a magnet wall and a GC and arranged in surface contact with the flat surfaces on both sides. This noise reduction device is configured such that the interior thereof is higher than the foam plastic filling or the external air pressure, and is in close contact with both sides as described above. Thereby, the vibration of the GC is attenuated and / or the GC is reinforced (supported).
In addition, although not related to the present invention, there are the following publicly known examples of techniques for reducing GC noise.

In [Patent Document 2], a GC is configured as a part of a vacuum container that accommodates a superconducting magnet.
As an example, a decoupling device is included in the coupling portion between the GC and the magnet to prevent the vibration of the GC from being transmitted to the vacuum vessel.
In [Patent Document 3], a silencer laminated plate structure that absorbs the acoustic vibration of the GC is provided on the inner surface of the magnet container to absorb and reduce the vibration of the GC.
In [Patent Document 4], a plurality of inclined spacers are arranged between the magnet and the GC, and are tightened in the axial direction, thereby suppressing the vibration by bringing the GC into close contact with the magnet.

Japanese Patent Laid-Open No. 11-076200 Japanese Patent Laid-Open No. 2001-104285 Japanese Patent Laid-Open No. 2003-051415 JP 09-000507 A

However, the above known techniques have the following problems.
[Patent Document 1] is a technology that assumes a horizontal magnetic field machine having a hollow cylindrical magnet shape. According to the shape of the embodiment, it is necessary to press the cylindrical GC evenly from the outside with a noise reduction device. Therefore, it cannot be applied to a counter-type magnet device. Regarding GC reinforcement, liquids such as water are packed between the GC and the magnet wall, but the contribution to GC reinforcement is very small due to the characteristics of water.

Other known techniques have the following problems.
In [Patent Document 2], the GC becomes weaker as the decoupling ratio is increased, so that the vibration amplitude of the GC itself increases and the fluctuation of the gradient magnetic field increases. For this reason, blurs and artifacts occur on the image and the image quality deteriorates.

In [Patent Document 3], it is difficult to completely shield the noise part including the cost, and it is difficult to obtain a substantial effect.
[Patent Document 4] is a technique that assumes a horizontal magnetic field machine, and a vertical magnetic field machine cannot take the same configuration.

  Therefore, the present invention has been made to solve the above problems, and in a vertical magnetic field type open MRI apparatus, by sufficiently suppressing the vibration of the GC due to the Lorentz force acting on the GC, the GC The purpose is to reduce the noise generated by vibration and the vibration of the static magnetic field source generated indirectly by the propagation of GC vibration.

In order to solve the above problems, the present invention is configured as follows. That is,
According to the first embodiment of the present invention, the static magnetic field generating means having the accommodating means for accommodating the static magnetic field generating source for generating the static magnetic field in the imaging region, and the gradient for generating the gradient magnetic field In the magnetic resonance imaging apparatus having a configuration in which the magnetic field generation means and the magnetic field generation means are arranged in pairs and face each other in the vertical direction or the horizontal direction,
The accommodating means has a rigidity improving structure, and the gradient magnetic field generating means is fixed substantially in close contact with the opposite surface side of the accommodating means.

Thereby, since the gradient magnetic field generating means can be firmly fixed to the housing means having a large rigidity, the vibration of the gradient magnetic field generating means can be reduced. As a result, the vibration of the storage means and the static magnetic field generation source in the storage means can be reduced, so that noise can be reduced and the influence on the image quality due to the slight fluctuation of the static magnetic field can be reduced.

According to a preferred second embodiment, in the magnetic resonance imaging apparatus of the first embodiment, a reinforcing member is arranged in close contact with the surface on the opposite surface side of the gradient magnetic field generating means, and the gradient magnetic field generating means is It is fixed on the opposed surface side of the housing means by penetrating the fixing member from the reinforcing member.
Thereby, the gradient magnetic field generating means and the accommodating means can be integrated, and the rigidity of the gradient magnetic field generating means can be improved. As a result, vibration and noise of the gradient magnetic field generating means can be reduced.

According to a preferred third embodiment, in the magnetic resonance imaging apparatus of the first or second embodiment, the gradient magnetic field generating means includes a main coil for generating the gradient magnetic field on the imaging region side. ,
A shield coil that reduces leakage of the gradient magnetic field to the static magnetic field generation source side, and an intermediate member disposed between the main coil and the shield coil. It penetrates and is fixed to the opposing surface side of the storage means .
Thereby, since the length of the fixing member can be shortened, the integration of the gradient magnetic field generating means and the accommodating means can be further improved. As a result, the vibration and noise of the gradient magnetic field generating means can be further reduced.

According to a preferred fourth embodiment, in the magnetic resonance imaging apparatus according to any one of the first to third embodiments, the accommodating means has a wall thickness on the opposite surface side that is opposite to the wall thickness on the opposite surface side. Is thicker than. Preferably, at least one fastening member that firmly fastens the opposite surface side and the opposite surface side is further disposed.
As a result, it is possible to increase the rigidity of the entire storage means by compensating for the decrease in rigidity of the storage means due to the fact that it is practically difficult to increase the wall thickness on the opposite surface side in order to secure an imaging region. As a result, it is possible to reduce the vibration of the housing means and reduce the vibration and noise of the gradient magnetic field generating means.

Further, according to a preferred fifth embodiment, in the magnetic resonance imaging apparatus of the first to fourth embodiments, the accommodating means is provided with at least one hole connecting the opposite surface side and the opposite surface side. It is done.
Thereby, since a void | hole serves as a rib, the rigidity by the side of the opposing surface of an accommodating means can be improved. As a result, it is possible to reduce the vibration of the housing means and reduce the vibration and noise of the gradient magnetic field generating means.

Also preferred according to the sixth embodiment, the magnetic resonance imaging apparatus of the fifth embodiment, the gradient magnetic field generating means in said holes so as to be tightly worn on a surface facing the accommodating means vacuo To be.
Thereby, the gradient magnetic field generating means can be brought into close contact with the accommodating means by atmospheric pressure. As a result, the integration of the storage means and the gradient magnetic field generation means can be improved while simplifying the structure for fixing the gradient magnetic field generation means to the storage means.

According to a preferred seventh embodiment, in the magnetic resonance imaging apparatus of the first to sixth embodiments, a nonmagnetic / insulating member is disposed between the housing means and the gradient magnetic field generating means.
Thereby, the distance between the gradient magnetic field generating means and the wall surface of the accommodating means can be increased, and the eddy current generated in the wall of the accommodating means by the gradient magnetic field can be reduced. As a result, artifacts and the like generated on the image due to eddy current can be reduced.

According to a preferred eighth embodiment, in the magnetic resonance imaging apparatus of the seventh embodiment, a nonmagnetic / conductive member is disposed between the housing means and the nonmagnetic / insulating member.
Thereby, the temporal fluctuation of the static magnetic field caused by the vibration of the static magnetic field generation source can be suppressed by the eddy current generated thereby. As a result, the image quality can be improved.

  According to the present invention, since the vibration of the GC generated when the GC is driven can be reduced, the influence of the vibration on the static magnetic field generation source can be suppressed. As a result, it is possible to take a high-quality image and reduce noise caused by GC vibration.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment of the invention, and the repetitive description thereof is omitted.
First, an outline of the MRI apparatus according to the present invention will be described. FIG. 6 shows an overall perspective view of an embodiment of a vertical magnetic field type (open type) MRI apparatus according to the present invention. This MRI apparatus uses a NMR phenomenon to obtain a tomographic image of a subject. As shown in FIG. 6, a gantry 51 that houses various devices for inducing a NMR phenomenon in a subject and receiving NMR signals. A table 52 for placing the subject, a power source for driving various devices in the gantry and a housing 53 for housing various control devices, and processing the received NMR signals to reconstruct a tomographic image of the subject. It consists of a processing device 54 for display, and each is connected by a power source / signal line 55. The gantry and the table are arranged in a shield room that shields a high-frequency electromagnetic wave and a static magnetic field (not shown), and the casing and the processing apparatus are arranged outside the shield room.

  FIG. 7 shows a block configuration diagram in which the configuration of the MRI apparatus in FIG. 6 is disassembled for each more detailed function. As shown in FIG. 7, the MRI apparatus includes a static magnetic field generation system 2, a gradient magnetic field generation system 3, a transmission system 5, a reception system 6, a signal processing system 7, a sequencer 4, and a central processing unit (CPU). 8 and configured.

  The static magnetic field generation system 2 generates a uniform static magnetic field in the space around the subject 1 in the direction of the body axis (horizontal magnetic field method) or in the direction orthogonal to the body axis (vertical magnetic field method). Around this is a normal or superconducting static magnetic field generation source. The static magnetic field generation system 2 is accommodated in the gantry 51.

  The gradient magnetic field generation system 3 includes a GC 9 wound in three axial directions of X, Y, and Z, and a gradient magnetic field power source 10 that drives each GC 9, and each coil according to a command from a sequencer 4 described later. By driving the gradient magnetic field power supply 10, gradient magnetic fields Gx, Gy, and Gz in the three-axis directions of X, Y, and Z are applied to the subject 1. More specifically, a slice direction gradient magnetic field pulse (Gs) is applied in one of X, Y, and Z to set the slice plane for the subject 1, and the phase encode direction gradient magnetic field is applied to the remaining two directions. A pulse (Gp) and a frequency encoding direction gradient magnetic field pulse (Gf) are applied, and position information in each direction is encoded in the echo signal. The GC 9 is housed in the gantry 51 and the gradient magnetic field power supply 10 is housed in the housing 53, respectively.

  The sequencer 4 is a control means that repeatedly applies a high-frequency magnetic field pulse (hereinafter referred to as “RF pulse”) and a gradient magnetic field pulse in a predetermined pulse sequence, and operates under the control of the CPU 8 to collect tomographic image data of the subject 1. Various commands necessary for the transmission are sent to the transmission system 5, the gradient magnetic field generation system 3, and the reception system 6. Furthermore, in the MRI apparatus of the present invention, the sequencer 4 includes means capable of measuring while changing the output of the RF pulse. The sequencer 4 is accommodated in the housing 53.

  The transmission system 5 irradiates an RF pulse to cause nuclear magnetic resonance to the nuclear spins of the atoms constituting the biological tissue of the subject 1, and includes a high frequency oscillator 11, a modulator 12, a high frequency amplifier 13, and a transmission side It consists of a high frequency coil 14a. The high-frequency pulse output from the high-frequency oscillator 11 is amplitude-modulated by the modulator 12 at a timing according to a command from the sequencer 4, and the amplitude-modulated high-frequency pulse is amplified by the high-frequency amplifier 13 and then placed close to the subject 1. By supplying to the high frequency coil 14a, the subject 1 is irradiated with the RF pulse. Generally, the high frequency coil 14a is accommodated in the gantry 51, and the others are accommodated in the casing 53.

  The receiving system 6 detects an echo signal (NMR signal) emitted by nuclear magnetic resonance of nuclear spins constituting the biological tissue of the subject 1, and receives a high-frequency coil 14b on the receiving side, a signal amplifier 15, and quadrature detection. And an A / D converter 17. The NMR signal of the response of the subject 1 induced by the electromagnetic wave irradiated from the high-frequency coil 14a on the transmission side is detected by the high-frequency coil 14b arranged close to the subject 1 and amplified by the signal amplifier 15, The quadrature phase detector 16 divides the signal into two orthogonal signals at the timing according to the command from the sequencer 4, and each signal is converted into a digital quantity by the A / D converter 17 and sent to the signal processing system 7. Generally, the device group constituting the receiving system 6 is accommodated in a gantry 51.

  The signal processing system 7 includes an external storage device such as an optical disk 19 and a magnetic disk 18 and a display 20 made up of a CRT or the like. When data from the receiving system 6 is input to the CPU 8, the CPU 8 performs signal processing, image processing, and image processing. Processing such as reconstruction is executed, and the resulting tomographic image of the subject 1 is displayed on the display 20 and recorded on the magnetic disk 18 or the like of the external storage device. The signal processing system 7 is accommodated in the processing device 54.

  In FIG. 7, the high-frequency coil 14a and the GC 9 on the transmission side are placed facing the subject 1 in the static magnetic field space of the static magnetic field generation system 2 in which the subject 1 is inserted. The high-frequency coil 14b on the receiving side is installed so as to face or surround the subject 1.

Currently, the radionuclide to be imaged by the MRI apparatus is a hydrogen nucleus (proton) which is a main constituent material of the subject as widely used in clinical practice. By imaging information on the spatial distribution of proton density and the spatial distribution of relaxation time in the excited state, the form of the human head, abdomen, extremities, etc., or biological functions are imaged two-dimensionally or three-dimensionally.
Next, the present invention will be described. In the present invention, the vibration amplitude of the GC is reduced by firmly fixing the GC to a static magnetic field generation source that has a rigid structure and is firmly formed. As a result, the vibration amplitude of the static magnetic field generation source is suppressed, and the generation of noise is also suppressed.

  A first embodiment in which the present invention is applied to the MRI apparatus will be described. FIG. 1 shows a cross-sectional view of a first embodiment of a vertical magnetic field type MRI apparatus using a superconducting magnet as a static magnetic field generation source. A uniform static magnetic field is generated at the center of the gantry by means of a static magnetic field generation source (superconducting coil) 201 arranged opposite to the top and bottom. In order to exert the superconducting characteristics, the superconducting coil 201 is disposed in a cryogenic container that maintains an extremely low temperature. This cryocontainer is contained in a vacuum chamber (accommodating means) 202 for shielding heat from the outside by heat insulation (refrigerators and helium tanks are omitted. In the case of a superconducting magnet using conductive cooling, Does not include a helium bath).

  The superconducting coil is supported at a predetermined position by a low-temperature support structure (not shown) fixed to the vacuum chamber 202. One or a plurality of connecting pipes 204 structurally support the upper and lower static magnetic field generation sources 201 at a predetermined interval, but if necessary, the electrical and temperature connection action of the upper and lower static magnetic field generation sources 201 Can also be performed.

  The GC 9 is fixed by a fixing member 203 on the inner side of the opposing surface of the static magnetic field generation source 201. Although the weight of GC9 varies considerably depending on the structure and material, it is generally relatively heavy, about 30 to 400 kg. In this embodiment, the vibration amplitude of the GC 9 is reduced by firmly fixing the GC 9 to the firmly formed vacuum chamber 202. As a result, the vibration amplitude of the static magnetic field generation source 201 is suppressed and the generation of noise is also suppressed.

  That is, by firmly fixing and integrating the GC 9 and the vacuum chamber 202, the total rigidity can be increased as compared with the case of the GC 9 alone. As a result, when the Lorentz force having the same strength is applied, it is possible to suppress the vibration amplitude to be smaller than that in the case of GC9 alone. In this embodiment, in order to improve the total rigidity, a plate made of a material having a high Young's modulus (for example, glass epoxy) is closely attached as a GC reinforcing material 205 to the opposite surface side of the GC. Adhesion or a mold integrated with GC can be used for this attachment.

  Further, by increasing the wall thickness on the opposite surface side of the vacuum chamber 202 as much as other design conditions allow, the total rigidity can be increased. Further, in FIG. 1, the fixing member 203 is disposed only at the peripheral portion of the GC 9, but it is desirable to dispose the fixing member 203 also on the inner peripheral side of the GC 9 in order to promote integration. Alternatively, it can be fixed by adhesion.

  The fixing member 203 for fixing the GC 9 is firmly fixed to the vacuum chamber 202 through the GC reinforcing material 205 and the GC 9 with the GC reinforcing material 205 interposed therebetween. The diameter of the through hole for the fixing member 203 in the GC 9 is desirably large enough that the side surface of the through hole does not contact the fixing member 203. This is because when the part where the fixing member 203 comes into contact with the side surface of the through hole is generated, the fixing state of the GC 9 varies depending on the location of the contact part and the degree of contact, and as a result, the vibration mode changes for each unit. This is because stable performance cannot be obtained. When a bolt is used as the fixing member 203, a screw hole is provided in the vacuum chamber 202 on the receiving side. If a sufficient thickness cannot be secured in the vacuum chamber, a pedestal 250 shown in FIG. 5 described below can be employed.

  FIG. 2 shows a second embodiment of the MRI apparatus to which the present invention is applied. For simplicity, only the lower side is shown, but the upper side has substantially the same structure, and each component is arranged vertically symmetrically with respect to the horizontal plane at the center in the imaging space. In the present embodiment, the GC 9 includes a main coil 213 for generating a gradient magnetic field from the imaging space side, an intermediate member 211, and a shield coil 214 for preventing the gradient magnetic field from leaking outside.

  In order to increase the total rigidity, the opposing surface side and the opposite surface side of the vacuum chamber 202 are firmly fastened by the vacuum chamber reinforcing material 210. The reason is as follows. That is, unlike the facing surface side, the anti-facing surface side has a relatively large size, so it is relatively easy to increase the wall thickness on this side. For this reason, it is possible to increase the rigidity of the facing surface side by fastening the facing surface side and the counter-facing surface side whose wall thickness is further increased by the vacuum chamber reinforcing material 210.

  Further, the fixing member 203 is fixed by a counterbore hole 212 portion provided in the intermediate member 211. Thereby, since the length of the fixing member 203 can be shortened, the integration of the GC 9 and the vacuum chamber 202 can be further improved, and the rigidity of the GC 9 can be improved. In FIG. 2, the GC 9 is composed of a main coil and a shield coil. Generally, since the main coil has a smaller diameter, the outer periphery can be configured as shown in FIG. On the inner peripheral side, a long fixing member 203 may be used as shown in FIG.

  However, in order to shorten the fixing member 203 on the inner peripheral side, a structure as shown in FIG. 5 is possible. FIG. 5 shows a partial cross section of the GC 9. A hole is formed in a part of the main coil 213 so that a fixing bolt as a fixing member 203 housed in the intermediate member 211 can be operated. When a bolt is used as the fixing member 203, a screw depth of a certain degree or more is required on the receiving side, but when a sufficient thickness cannot be secured in the vacuum chamber, a pedestal 250 shown in FIG. 5 described below is adopted. be able to.

  Here, in the second embodiment, it has been explained that both the three-layer structure of GC9 and the structure of the vacuum chamber 202 with the vacuum chamber reinforcing material 210 are included, but these structures do not necessarily have to be implemented together. Either one of them may be used.

  FIG. 3 shows a third embodiment of the MRI apparatus to which the present invention is applied. In the present embodiment, a hole 251 is provided in the central portion in order to strengthen the opposing surface side of the vacuum chamber 202. Since the air holes 251 serve as ribs, the rigidity of the facing surface wall can be improved. Further, the position of the hole 251 is not limited to the center portion, and may be an off-center position, or a plurality of holes may be provided. The provided holes 251 can also be used as a route for cables and cooling pipes. Alternatively, it is possible to fix the GC9 to the vacuum chamber 202 by atmospheric pressure by increasing the adhesion between the holes 251 and GC9 and drawing the inside of the holes 251 to a vacuum. In this case, there is an advantage that the structure related to the fixed portion on the GC9 side is simplified.

Further, a nonmagnetic / insulating member 220 and a nonmagnetic / conductive member 221 are disposed between the GC 9 having the same structure as that of the second embodiment and the vacuum chamber 202. The non-magnetic / conductive member 221 is disposed in order to suppress the time variation of the static magnetic field caused by the vibration of the static magnetic field generation source 201 by eddy current (Patent Document 5). For this reason, materials with high electrical conductivity such as aluminum and copper are preferred. It is also possible to provide a hole in this conductor and also serve as a tray for arranging shim materials. The thickness of the nonmagnetic / conductive member 221 is preferably about several millimeters to 30 millimeters.
WO02 / 071942 Publication

The non-magnetic / insulating member 220 is arranged to prevent the eddy current from being generated when the coil pattern portion of the GC 9 and the electric conductor portion such as the non-magnetic / conductive member 221 are too close to deteriorate the image quality. (The shield coil pattern is designed to prevent eddy currents due to GC, but it cannot be sufficiently suppressed if the distance to the conductor is too close.)
The thicker the non-magnetic / insulating member, the higher the effect of suppressing eddy currents. However, in order to secure an open space, it is necessary to make other components thinner. Therefore, practically, about several millimeters to about several tens of millimeters are preferable. In addition, by arranging a shim coil in this part by a mold or the like, it is possible to effectively utilize the dimension.

  In the third embodiment, the members inserted between the GC 9 and the vacuum chamber 202 need to be firmly integrated with the wall of the vacuum chamber 202 including the GC 9. For this reason, it is possible to fix the nonmagnetic / conductive member 221 and the vacuum chamber 202 in advance by bonding or welding, or to form the clad material. Here, the clad material is a composite material for rolling different metals into a single plate to bring out the respective material properties. In the present embodiment, a stainless steel material that is a general material of the vacuum chamber 202 and a material having high electrical conductivity such as aluminum or copper used for the non-magnetic / conductive member 221 are used as a composite material. As a result, the purpose of each member is achieved, and the rigidity is improved by integrating the two. Further, the non-magnetic / insulating member 220 and the GC 9 can be integrated by bonding, molding, or the like, so that workability such as attachment is improved.

  FIG. 4 shows a fourth embodiment of an MRI apparatus to which the present invention is applied. An enlarged view of the central fixing part of (a) is shown in (b). In the present embodiment, a case where a split nut 301 is used as a structure for attaching the GC 9 is shown. A split nut 301 is fixed in advance to the wall of the vacuum chamber 202 by welding or bonding. Here, the nonmagnetic / insulating member 220 is fixed to the GC9. By inserting a tapered screw 302 into the split nut 301, the outer periphery of the nut expands and is fixed by pushing the inner wall of the nonmagnetic / insulating member 220. The same applies when the inner peripheral screw on the nut side is tapered instead of the screw. In the case of this fixing method, since the diameter of the hole provided in the main coil or the intermediate member can be reduced, there is an advantage that GC manufacture becomes easy. Although the nonmagnetic / conductive member 221 is not shown in FIG. 4, the illustration is omitted to clarify that a configuration without the nonmagnetic / conductive member 221 is possible.

  FIG. 5 shows an embodiment in which a fixing bolt is used as a fixing member and the fixing bolt is fixed using a pedestal. A hole for receiving the head portion of the fixing bolt 203 is formed in the photographing space side of the intermediate member 211, and a hole through which the lower neck portion of the fixing bolt 203 can be penetrated in the remaining portion of the intermediate member 211 and the shield coil 214. deep. The through hole preferably has an inner diameter such that the side surface does not come into contact with the fixing bolt 203. Further, a screw hole is provided in the vacuum chamber 202 on the receiving side. Therefore, it is necessary to have a screw depth of a certain level or more in the vacuum chamber 202. However, if a sufficient thickness cannot be secured in the vacuum chamber 202, the pedestal 250 is installed on the opposite surface side of the vacuum chamber 202 and the nonmagnetic / insulating member 220 Is provided with a hole that can accommodate the pedestal. With these configurations, the intermediate member 211 and the shield coil 214 are sandwiched and fixed by the head portion of the fixing bolt 203.

  The above describes the embodiment in which the present invention is applied to a vertical magnetic field type MRI apparatus using a superconducting magnet as a static magnetic field generation source. Is possible. For example, a similar structure can be applied to a normal conducting coil. Further, a configuration in which a pair of static magnetic field generation sources are arranged to face each other in the horizontal direction is also possible.

  Furthermore, although each embodiment was demonstrated separately, the structure which combined several embodiment is also possible. For example, by combining the second and third embodiments, the vacuum chamber 202 may be provided with both the vacuum chamber reinforcing material 210 and the air holes 251 to increase the rigidity of the vacuum chamber 202. Alternatively, the rigidity of the GC 9 may be improved by combining the first and second embodiments and covering the GC 9 of the second embodiment with the GC reinforcing material 205 of the first embodiment.

The figure which shows sectional drawing of 1st Embodiment of the MRI apparatus to which this invention is applied. The figure which shows sectional drawing of the lower part of 2nd Embodiment of the MRI apparatus to which this invention is applied. The figure which shows sectional drawing of the lower part of 3rd Embodiment of the MRI apparatus to which this invention is applied. The figure which shows sectional drawing of the lower part of 4th Embodiment of the MRI apparatus to which this invention is applied. The figure which shows one Embodiment which attaches a base to the upper part of a vacuum chamber and bolts a gradient magnetic field coil. 1 is an overall perspective view of an embodiment of a vertical magnetic field type (open type) MRI apparatus according to the present invention. FIG. The figure which shows the block structure which decomposed | disassembled the structure of the MRI apparatus of FIG. 6 for every more detailed function.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Subject, 2 ... Static magnetic field generation system, 3 ... Gradient magnetic field generation system, 4 ... Sequencer, 5 ... Transmission system, 6 ... Reception system, 7 ... Signal processing system, 8 ... Central processing unit (CPU), 9 ... Gradient magnetic field coil, 10 Gradient magnetic field power source, 11 High frequency transmitter, 12 Modulator, 13 High frequency amplifier, 14 a High frequency coil (transmitting coil), 14 b High frequency coil (receiving coil), 15 Signal amplifier, 16 ... Quadrature phase detector, 17 ... A / D converter, 18 ... Magnetic disk, 19 ... Optical disk, 20 ... Display, 51 ... Gantry, 52 ... Table, 53 ... Housing, 54 ... Processing device

Claims (9)

A pair of a static magnetic field generation means having a storage means for storing a static magnetic field generation source for generating a static magnetic field in the imaging region and a gradient magnetic field generation coil for generating a gradient magnetic field are paired vertically. In a magnetic resonance imaging apparatus having a configuration arranged opposite to each other in a horizontal direction or a horizontal direction,
The accommodating means has a rigidity improving structure,
A reinforcing member is disposed in close contact with the surface on the opposite surface side of the gradient magnetic field generating coil,
Said gradient magnetic field generating coils, by a fixing member penetrating through the reinforcing member, the surface facing the accommodating means, the entire surface of the surface facing the said housing means of said gradient magnetic field generating coil is substantially in close contact, the fixed A magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 1.
The gradient magnetic field generating coil includes a main coil for generating the gradient magnetic field on the imaging region side,
A fixed coil that includes a shield coil that reduces leakage of the gradient magnetic field to the static magnetic field generation source side, and an intermediate member that is disposed between the main coil and the shield coil, and passes through the intermediate member. A magnetic resonance imaging apparatus, wherein the magnetic resonance imaging apparatus is fixed to an opposing surface side of the housing means by a member . The magnetic resonance imaging apparatus according to claim 1 or 2,
The magnetic resonance imaging apparatus according to claim 1, wherein the housing means has a wall thickness on the opposite surface side larger than a wall thickness on the opposite surface side . The magnetic resonance imaging apparatus according to any one of claims 1 to 3,
The magnetic resonance imaging apparatus according to claim 1, wherein at least one fastening member that firmly fastens the opposing surface side and the counter-facing surface side is disposed in the housing means . The magnetic resonance imaging apparatus according to any one of claims 1 to 4,
2. The magnetic resonance imaging apparatus according to claim 1, wherein the accommodating means is provided with at least one hole for fastening the opposite surface side and the opposite surface side . The magnetic resonance imaging apparatus according to claim 5.
The magnetic resonance imaging apparatus according to claim 1, wherein the air hole is evacuated so that the gradient magnetic field generating coil is in close contact with the facing surface of the housing means . The magnetic resonance imaging apparatus according to any one of claims 1 to 6,
A magnetic resonance imaging apparatus , wherein a nonmagnetic / insulating member is disposed between the housing means and the gradient magnetic field generating coil . The magnetic resonance imaging apparatus according to claim 7.
A magnetic resonance imaging apparatus , wherein a nonmagnetic / conductive member is disposed between the housing means and the nonmagnetic / insulating member . A static magnetic field generating means having an accommodating means for accommodating a static magnetic field generating source for generating a static magnetic field in the imaging region and a gradient magnetic field generating means for generating a gradient magnetic field are paired vertically. In a magnetic resonance imaging apparatus having a configuration arranged opposite to each other in a horizontal direction or a horizontal direction,
The accommodating means is provided with at least one hole for fastening the opposite surface side and the opposite surface side.
The magnetic resonance imaging apparatus according to claim 1, wherein the inside of the hole is evacuated so that the gradient magnetic field generating means is fixed in close contact with the opposing surface side of the housing means .

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